Apparatus for vapor phase heating of traffic line paints

ABSTRACT

This disclosure relates to an apparatus for applying a marking liquid medium to a substrate and more particularly traffic line paints to roadways, and includes vaporizer means for heating a heat transfer liquid to the saturation temperature of the liquid and its vapor to produce a wet mixture thereof, and condensing means for heating the marking liquid medium by the wet mixture at generally the aforesaid saturation temperature to thereby accurately control the temperature of the marking liquid medium. The vaporizer and condenser means are portions of a closed fluid system which additionally includes as a portion thereof a liquid cooled engine having a cooling system with hot and cold sides, and the latter cooling system being connected to receive return flow from the condenser means into its cold side while transferring the heat transfer liquid from its hot side to the vaporizer means.

Currie Apr. 9, 1974 APPARATUS FOR VAPOR PHASE HEATING OF TRAFFIC LINEPAINTS Primary Examiner-Kenheth W. Sprague Attorney, Agent, orFirmAlfred W. Breiner [75] Inventor: Adam Currie, Huntingdon, Pa. [57]ABSTRACT Assigneei Baltimore Paint Chemical This disclosure relates toan apparatus for applying a COPPM'QUOH, Baltlmofe, marking liquid mediumto a substrate and more partic- [22] Elem Dec. 15, 1971 ularly trafficline paints to roadways, and includes vaponzer means for heating a heattransfer liquid to the PP N06 208,186 saturation temperature of theliquid and its vapor to produce a wet. mixture thereof, and condensingmeans [52 us. c1. 122/33, 239/135 fer heating the making e mediumhy the51 1111.01. F22b 1/16 at generally the efereeeld Setureheh temPerehlre58 Field of Search ..94/1.5, 44; 239/129, 130, to e y aeeuretely eemrelthe Eemperewre ef the 239/134, 135,.136, 139, 150; 122/33 marking liquidmedium. The vaporizer and condenser means are portions of a closed fluldsystem which ad- [56] References Cited ditionallly includes as 2;portiortl theretzlfi'ahliquid soolig engine avmg a coo mg sys em v v1 0an co UNITED STATES PATENTS sides, and the latter cooling system beingconnected to 3992325 6/1963 f et 239/129 X receive return flow from thecondenser means into its Mner et cold side while transferring the heattransfer liquid 2:980:339 4/196! Bok et al. 239/135 from hot to thevaporzer means- 7 Claims, 1 Drawing Figure COLD PA '5 f FROM sll w r f"p L4 couoenseiz {l f; 25f] I H1 11 a, I I 3 -27, E vApomzeRf l? l i V ll4' l /l l 32 I 3 I 3 I J :2 v 36 l} 38 v uorg n fl RADIATOR BYPASSggpimrhs L3 39 com sme aggggggtgg LlQUlD COOLED ENGlNE Hor Sl DE TPATENTEUAPR 9 I974 kzzu Sou BY M ATTORNEYS APPARATUS FOR VAPOR PHASEHEATING OF TRAFFIC LINE PAINTS FIELD or INVENTION AND BACKGROUND Thepresent invention is directed to an apparatus for applying a markingliquid medium to a substrate. More particularly, the invention isdirected to an apparatus for applying traffic and/or pedestrian linepaints to roadways or walkways at an elevated temperature to ensurerapid drying. The device permits uniform and accurate temperaturecontrol of the marking liquid medium over a wide range of applicationtemperatures.

Conventional means are known for applying traffic or pedestrian linepaints to roadways and/or walkways by first elevating the temperature ofthe paint prior to its application to a suitable substrate. The elevatedtemperature decreases the drying time of the paint. As the needfor morerapid drying traffic paints is increased, the trend is toward highertemperature applications. At higher temperatures, paints becomeincreasingly heat sensitive and require extremely close temperaturecontrol. Above a pre-determined temperature the paint deteriorates;whereas below the prede-' termined temperature the required drying timeincreases, precluding any substantial fluctuation in applicationtemperatures. Further, to obtain a constant thickness of film for agiven speed and pressure of application, it is againnecessary that thetemperature be maintained within a narrow range.

The conventional prior art stripping or paint applying machinesgenerally use hot water, hot oil, and/or hot air as the heat transferfluid for elevating the temperature of the paint prior to itsapplication. However, such devices using the aforesaid fluids includeone or more disadvantages which render the same particularly unsuitablefor applying paints to streets and highways subject to heavy trafficflow necessitating very rapid dry to reduce traffic congestion, etc.More specifically, hot water systems are undesirable since they can onlymake use of the sensible heat and, accordingly, cannot raise thetemperature of the paint above a finite level. Since the temperaturerange of such systems is limited, the decrease in drying time of thepaints is limited. While hot oil or hot water systems can provide thenecessary high temperature for application, accurate temperature controlis difficult. Fluctuations in temperature occur in such systems and, asa result of the heat sensitivity of the paints, scorching of the paintand/or clogging or plugging of the equipment being utilized occurs,particularly in applications where the paint spraying is an intermittentprocess. In the latter instances overheating is particularly pronouncedwhen the spray gun or the applicator is shut-off, enchancing thepossibility of paint scorching and/or clogging or plugging of thesystem.

OBJECTS OF THE INVENTION Accordingly, it is a primary object of thepresent invention to avoid the disadvantages heretofore noted inconventional traffic line painting machines by (l) employing vaporizermeans for heating a heat-transfer liquid (such as water) to itssaturation temperature to produce at least a wet mixture thereof; and(2) utilizing condenser means for heating the paint through the media ofthe wet mixture at generally the saturation temperature to therebyaccurately control the temperature of the paint avoiding scorching,plugging, etc.

A further object of this invention is to provide a novel apparatus ofthe type heretofore set forth wherein the vaporizer and condenser meansare portions of a closed fluid system, and means are provided forregulating the pressure and/or temperature of the fluid system to varythe saturation temperature thereby adapting the apparatus for use with avariety of different heat-transfer liquids.

Still another object of this invention is to provide a novel apparatusof the type described wherein the closed fluid system includes as aportion thereof a cooling system of a liquid cooled engine having hotand cold sides, and the engine cooling system being connected to receivereturn flow into its cold side while directing the heat transfer liquidfrom its hot side to the varporlzer means.

DRAWING AND DETAILED DESCRIPTION OF THE INVENTION With the above andother objects in view which will appear hereinafter, the nature of theinvention will be more clearly understood by reference to the followingdetailed description, the appended claimed subject matter, and theaccompanying drawing.

In the drawing, the single FIGURE is a highly schematic illustration ofthe apparatus of this invention for applying a marking liquid medium toa substrate and illustrates a vaporizer for heating a heat-transferliquid (water) to the saturation temperature of the liquid and its vaporto produce a wet mixture thereof and transferring the wet mixture tocondensor means for heating the marking liquid medium to therebyaccurately control the temperature thereof.

The phrase saturation temperature of the liquid and vapor as used hereinmeans the temperature of the boiling process of a particular liquid at aparticular pressure where vapor exists and liquid remains. The mixtureof such liquid and its vapor is referred to as a wet mixture. Of primaryimportance with respect to the present invention is a characteristic ofthe saturation temperature, in that the temperature of the liquid andany vapor thereof remains constant as long as there is liquid present.This statement assumes a condition of equilibrium. In practicalapplication, small difierences of temperature in the various parts ofthe wet mixture may exist. These differences are not sufflcient to bedetrimental to the claimed system.

The constant and accurate control of the temperature realized using thepresently described system, therefore, is based on the characteristicthat the temperature of the liquid and vapor remains constant at thesaturation temperature of the liquid and vapor as long as there is anyliquid present. Experiments have shown that if heat is transferred toheat-sensitive traffic paints at constant temperature in accordance withthe presently disclosed system, scorching is eliminated, plugging and/orclogging does not occur, and constant line thickness can be maintainedeven in the presence of intermittent cut-off of the system as usuallyoccurs. Moreover, by adjusting the pressure and/or liquid transferfluid, the degree of the constant temperature can be varied over a widerange.

Referring to the drawing, an apparatus 10 is provided which includes asa portion thereof a vapor phase system 11 including heat-transfer means12 in the form of a vaporizer for heating a liquid W such as water,ethylene glycol, an aqueous salt solution, or other heattransfer liquidsto the saturation temperature of the liquid and vapor to produce a wetmixture M therefrom. The vaporizing means 12 includes a suitable housing13 internally of which are coils 14 through which the liquid W istransformed into the wet mixture M by flames F from a burner 15 having aconduit 16 coupled to a gas, oil, or similar source of combustible fluidwith a suitable valve 17 being provided to adjustably regulate the flameF through a conventional solenoid l8 operable in response to aconventional sensing mechanism 20 over conductor means 21. The valve 17,therefore, operates in response to the temperature of the wet mixture Mas the wet mixture M flows through first conduit means 22 to secondheating means in the form of a condenser 23. The conduit 22 may includea suitable conventional safety valve 24 and a pressure gauge 25 sincethe pressure within the system 11 as indicated by the pressure gauge 25will establish the saturation temperature of the liquid W.

The condenser 23 may be of a conventional surface condenser type andinclude an outer housing or shell 26 housing metallic condenser tubes 27having an inlet 28 coupled to a source (not shown) of paint preferablyretained in a reservoir and an outlet 30 coupled to spray nozzles orsimilar applicators (not shown) through a valve 31. The valve 31 may beselectively positioned to feed the paint spray nozzles, close flowthereto, or redirect the heated paint over a conduit 32 to the reservoir(not shown) for subsequent recirculation into the condenser 23 throughthe inlet 28. The paint or similar liquid marking medium is circulatedcontinuously through the condenser tubes 27 and is heated as it picks upand carries away the heat released by the wet mixture M resulting in theretransformation of the wet mixture to its liquid form W as condensate.As was heretofore noted, since the wet mixture is at its saturationtemperature, the temperature within the condenser 23 will besubstantially uniform at all times so long as the pressure is maintainedas desired which can obviously be effected by suitably regulating thevalve 24. In this manner the paint transmitted through the condensertubes 27 can be heated to a precise temperature and maintained thereatirrespective of the intermittent use of the apparatus 10, including atotal shut-off or closing of the spray nozzles (not shown).

Second conduit means 33 which may or may not include a conventionalbooster pump 34 are provided for returning the liquid W to the coils 14of the vaporizer 12 through a bypass valve 35. The bypass valve 35 is atthe juncture of four legs 36 through 39 of the conduit means 33 andfunctions when positioned at one setting to direct the liquid W directlyfrom the leg 36 into the leg 37 to bypass a conventional liquid cooledengine 40 of a truck or like vehicle including its own cooling systemwhich includes a pump 41, a fan 42, and a radiator 43. In a secondposition of the bypass valve 35 the leg 36 is directly connected to theleg 38 and the liquid W returning from the condenser 23 is fed directlyinto the radiator 43 through the leg 36, the bypass valve 35, and theleg 38. The liquid circulates through the radiator and is introduced bya conduit 44 into the cold side of the jacketed cooling system of theengine 40 while the hot side thereof is placed in fluid communicationwith the coils 14 of the vaporizer through the leg 36, the bypass valve35, and the leg 37. By this construction the apparatus 10 may beoperated irrespective of the on or off condition of the engine 40; and,for that matter,

when associated with mobile vehicles devoid of liquidcooled engines orsimply portable vehicles, the bypass valve 35 could be eliminated andthe legs 36, 37 of the conduit means 33 would be directly coupled toeach other without in any way affecting the operation of the system 11to heat the paint in the condenser tubes 27 at generally the saturationtemperature of the wet mixture M.

The essence of this invention insofar as the over-all vapor phase system11 is concerned is the use of the vaporizer or vapor generator 12, thecondenser 23, and as necessary ancillary equipment to'transfer heat atits saturation temperature either as a wet mixture M or as a vapor up tobut not beyond the saturated vapor state. As a result, a very uniformand constant paint temperature issuing from the conduit 30 is maintaineddue to the constant temperature of the condensing wet mixture M with, ofcourse, the saturation temperature being readily determined independence upon primarily the particular liquid W involved, the pressureof the system 11 and, obviously, the speed of application of the paint.As an example, if it is assumed desirable to apply a traflic line of thepaint 4 inches wide and 0.015 inch thick at a speed of 2 miles per hour,then the B.T.U.s per hour required for such a paint line would be for180F. paint at 60F. ambient 13,800 B.T.U.s per hour. A vapor pressure of10 psig is generated at the vaporizer 12 and since the wet mixtureand/or vapor will contain 952 B.T.Us per pound, then the condenser 23will have to condense:

13,800/952 14.5 lbs./hr.

and the pump 34 will return this condensate to the vaporizer 12.

As indicated hereinbefore, by varying the pressure of the heat-transferliquid, the temperature which is to be maintained constant can becontrolled within a wide range. Thus, where liquid W in the system 11 iswater and the pressure is atmospheric, i.e., 14.696 lbs./in-. thesaturation temperature will be approximately 212F. However, if thepressure is increased, the saturation temperature of water will also beincreased. For example, when operating at pounds per square inch ofpressure, the water will boil at 327.8F., thereby increasing thesaturation temperature of the system and, accordingly, increasing thetemperature at which the paint is maintained. The constant temperatureof the system and, accordingly, the temperature of the paint can befurther varied by utilizing a liquid other than water. Thesemodifications will be apparent to one skilled in the art.

While preferred forms and arrangements of parts have been shown inillustrating the invention, it is to be clearly understood that variouschanges in details and arrangement of parts may be made withoutdeparting from the spirit and scope of this disclosure.

What is claimed:

1. In an apparatus for applying paint for marking traffic lines or thelike to a road surface, the improvement comprising means for heating aheat-transfer liquid to the saturation temperature of the liquid and itsvapor to produce a wet mixture thereof, and means for conducting saidpaint in indirect heat transfer relationship with said wet mixture for atime sufficient to heat said paint to generally said saturationtemperature, to thereby accurately control the temperature of saidpaint.

2. The improvement in the apparatus as defined in claim 1 wherein saidheating means include a vaporizer and condenser.

3. The improvement in the apparatus as defined in claim 2 wherein saidheating means is a portion of a closed fluid system, and includes meansfor regulating the pressure of said fluid system to vary the saturationtemperature of said heat-transfer liquid.

4. The improvement in the apparatus as defined in claim 3 wherein saidheating means is a portion of a closed fluid system, and said closedfluid system includes first conduit means for the flow of said wetmixture from said vaporizer to said condenser, and second conduit meansfor return flow from said condenser to said varporizer.

5. The improvement in the apparatus as defined in claim 3 wherein saidheating means is a portion of a closed fluid system, said closed fluidsystem includes first conduit means for the flow of said wet mixturefrom said vaporizer to said condenser, second conduit means for returnflow from said condenser to said vaporizer, a liquid cooled enginehaving a cooling system with hot and cold sides, and said liquid cooledengine cooling system being a portion of said closed fluid system andbeing connected to receive return flow into its cold side through saidsecond conduit means and direct the heat-transfer liquid from its hotside to said vaporizer through said second conduit means.

6. The improvement in the apparatus as defined in claim 3 wherein saidheating means is a portion of a closed fluid system, and said closedfluid system includes first conduit means for the flow of said wetmixture from said vaporizer to said condenser, second conduit means forreturn flow from said condenser to said vaporizer, a liquid cooledengine having a cooling system with hot and cold sides, said liquidcooled engine cooling system being a portion of said closed'fluid systemand being connected to receive return flow into its cold side throughsaid second conduit means and direct the heat-transfer liquid from itshot side to said vaporizer through said second conduit means, and meansfor by-passing said engine including the cooling system thereof andeffecting return flow directly from said condenser to said vaporizer.

7. The improvement in the apparatus as defined in claim 1 includingmeans responsive to the temperature of said wet mixture to regulate saidheating means.

1. In an apparatus for applying paint for marking traffic lines or thelike to a road surface, the improvement comprising means for heating aheat-transfer liquid to the saturation temperature of the liquid and itsvapor to produce a wet mixture thereof, and means for conducting saidpaint in indirect heat transfer relationship with said wet mixture for atime sufficient to heat said paint to generally said saturationtemperature, to thereby accurately control the temperature of saidpaint.
 2. The improvement in the apparatus as defined in claim 1 whereinsaid heating means include a vaporizer and condenser.
 3. The improvementin the apparatus as defined in claim 2 wherein said heating means is aportion of a closed fluid system, and includes means for regulating thepressure of said fluid system to vary the saturation temperature of saidheat-transfer liquid.
 4. The improvement in the apparatus as defined inclaim 3 wherein said heating means is a portion of a closed fluidsystem, and said closed fluid system includes first conduit means forthe flow of said wet mixture from said vaporizer to said condenser, andsecond conduit means for return flow from said condenser to saidvaporizer.
 5. The improvement in the apparatus as deFined in claim 3wherein said heating means is a portion of a closed fluid system, saidclosed fluid system includes first conduit means for the flow of saidwet mixture from said vaporizer to said condenser, second conduit meansfor return flow from said condenser to said vaporizer, a liquid cooledengine having a cooling system with hot and cold sides, and said liquidcooled engine cooling system being a portion of said closed fluid systemand being connected to receive return flow into its cold side throughsaid second conduit means and direct the heat-transfer liquid from itshot side to said vaporizer through said second conduit means.
 6. Theimprovement in the apparatus as defined in claim 3 wherein said heatingmeans is a portion of a closed fluid system, and said closed fluidsystem includes first conduit means for the flow of said wet mixturefrom said vaporizer to said condenser, second conduit means for returnflow from said condenser to said vaporizer, a liquid cooled enginehaving a cooling system with hot and cold sides, said liquid cooledengine cooling system being a portion of said closed fluid system andbeing connected to receive return flow into its cold side through saidsecond conduit means and direct the heat-transfer liquid from its hotside to said vaporizer through said second conduit means, and means forby-passing said engine including the cooling system thereof andeffecting return flow directly from said condenser to said vaporizer. 7.The improvement in the apparatus as defined in claim 1 including meansresponsive to the temperature of said wet mixture to regulate saidheating means.